TWO KNOTS AT FLANK SPEED?
 

I'm on the surface at ahead full. To conserve fuel is dive to PD. My speed decreases from about 17 knots to 2 @ flank speed! If this is normal as the battery is drained, I haven't noticed this before. :hmmm:

What's wrong?

Yep, as your batteries lose charge, the engine/boat speed falls away till you can barely move.

Thank u, sir!

I guess i just didn't notice it before. Normally when my patrol area was fairly close to port I cruised on the surface at full time compression. Now, the PA is getting a lot farther away and I'm diving to PD to conserve full and speed reduces quickly at full time compression. So, I thought something was wrong.:doh:....:)

My two cents:
three things come to mind
a) You mention to have set speed at "ahead full". This uses up a lot of fuel. The farther you are sent out to, the more important is to conserve fuel. So, just like driving a car, try to go slower. I now use ahead 1/3, except for combat related situations (including dashing to a meeting point with a potential target);
b) Just like any toy or portable electric equipment, as the battery charge drains, less power is available;
c) When the batteries need recharging, only one engine is driving the boat while the other is used as a generator to recharge the batteries, hence the boat speed is slower while recharging. My type VIIc cruises at 8 knots in "ahead 1/3" while recharging, and speeds up to 10 knots when the batteries are recharged and the other engine switches for propelling the boat.

Side note: I avoid prolonged runs on anything higher than "ahead standard" for durability reasons. Although I never had any problems with engines in SH3, in SH2 I run into problems with engines if pushing them in "ahead full" or "ahead flank" for long stretches - "engines are overheating!" and if I neglect it - "engines damaged!" - which will then take some (more realistic) 3 or more hours to fix with the boat stoped.

Edit: I re-read your comments and it strikes me that you try to sail out to the big blue ocean submerged, using the batteries. You should check the submarine specs, they show range for surface (diesel engines) and submerged (electric motors). You will notice the range in submerged mode is significantly reduced compared to surfaced mode. Electric motors should only be used for situations that require you to be submerged. Until the advent of nuclear power, electric motors on submarines were never intended to be used for long cruising stretches. The outstanding durability of the type XXI batteries was due mainly to them being so many, practically the whole bottom section of the boat. A lot more can be said about conserving resources and speeds and specs, but I will not spoil the fun of discovering these things for you :)

Does it happen during every patrol you run?

Do you recharge your batteries while on the surface?

Are using SH3 Commander , and if yes do you have the mulfuction and sabotage option checked?

This has been added to SH3 with the exellent H.sie's V16B1 realism pack and Stiebler's add ons.

Running on batteries won't conserve fuel. R/L, it takes more energy to charge the batteries than you can get out of them, usually about 15-25% more. (This is the myth of the electric car.) I doubt the devs actually modeled this, but it's built into ranges and speeds. You use just as much fuel going slow on one engine while the other recharges the batteries as you do going much faster on two engines at normal propulsion. And you go slower still on batteries. So the distance traveled on a "tank of gas" decreases the more you use the batteries.

All WW2 submarines were spec'ed to deliver optimum cruise radius at 10 knots. So that's what the builders delivered. Set you speed to 10 kts and you will see greatly improved range. That's what the R/L sub skippers did, and it works in the game. Also, check with the Nav officer on range remaining. It'll quickly show you optimum cruising speed.

That was my thought :hmmm:

True in real life, and true in SH4. Not true in SH3. Battery charging in the game doesn't work properly, and does indeed give you an advantage, or so many reported in the early days. I've never tried it myself, since it's unrealistic even if it does work.

Charging batteries in SH3 does not consume fuel. Doesn't really make a difference, if not abused.

You are saying, Steve, that fuel consumption in SH3 is based on speed through the water and not on engine settings? So you can run at Flank speed in a heavy sea and use less fuel than at Standard in calm weather? That is so counterintuitive and so wrong that it ought to be a priority item for fixing. I hope someone is working on it! (Stiebler, can you help? I'm guessing it would require a code patch.)

Do you remember the scene in Das Boot, when Kriechbaum mentiones in the heavy storm "we don't make any speed/progress over ground" and the Kaleun orders to dive? Running on batteries did save fuel under certain circumstances, because they where able to move at all. It happened in real life too.

No. I'm only saying that running underwater then surfacing to recharge your batteries will actually extend your range in the game. The energy is not lost as it should be when recharging. Yes, this is totally unrealistic, and it was fixed for SH4.

May I suggest you read Dick O'Kane and Ned Beach, two American submarine skippers of WW2. Both describe running submerged in storms. Not to mske more progress, but to reduce the wear and tear on the boat and, equally important, on the crew. IIRC, O'Kane nearly had a lookout killed by being battered by a huge wave. The notion that somehow a WW2 submarine could actually make better speed submerged than on the surface is not borne out by the historical record. Even a u-boat could make 4-5 knots in bad weather on the surface, and could not sustain that speed submerged for more than an hour or so. Storms at sea often last for days.

Imagine the scene...you surface and drift because your out of fuel but suddenly as if by magic, your batteries are charged up.

To each their own I suppose but I certainly don't subscribe to that.

If you run out of fuel simply press the Esc key (if you must) and hyper drive back to base.

For me in that occasion : Scuttle the U-boot and surrender to the Allied Forces , if you are lucky enough.